After more playing around with the appliques last night, here is what I've come up with. The appliques are all fuse-tacked in place. I didn't want to take the top down from the design wall and fuse-tack on my ironing board for fear of the appliques shifting out of place. The problem is that my design wall is insulation board and I didn't think it was a good idea to use the iron on it with just the fabric separating it from the iron heat. My solution was to take a piece of Insul-Bright by The Warm Company, and tuck it underneath the quilt top, pin it in place, and then fuse-tack the appliques down. It worked like a charm - no damage to the insulation board. I'm now planning on covering the entire design wall in Insul-Bright underneath a layer of cotton batting.
I'm still pondering border options - haven't come to a conclusion there. I have decided to back the entire top with Decor-Bond then load it onto the longarm for the thread painting. I've done that with one other quilt top and it worked great.
I will probably back the entire top with Decor-Bond by Pellon, then load it onto the longarm frame to do the thread work. I have 3 weeks until quilt entries are due for the guild show, so I need to get busy.